NADPH oxidase derived ROS promote arterial contraction in early postnatal rats by activation of L-type voltage-gated Ca2+ channels.

Reactive oxygen species (ROS) produced by NADPH oxidase promote contraction of peripheral arteries, which is especially pronounced in early postnatal period in comparison to adulthood, but the mechanisms of such vasomotor influence are poorly understood. We tested the hypothesis that Rho-kinase and protein kinase C (PKC) mediate procontractile influence of NADPH oxidase derived ROS in peripheral artery of early postnatal rats. In addition, we evaluated the involvement Src-kinase and L-type voltage-gated Ca²⁺ channels (LTCC) into procontractile influence of ROS, produced by NADPH oxidase, because of their known interplay with Rho-kinase and PKC pathways. Saphenous arteries from 11- to 15-day-old male rats were studied using quantitative PCR, isometric myography and lucigenin-enhanced chemiluminescence. Arterial tissue of early postnatal rats contained Nox2, Nox4, Duox1 and Duox2 mRNAs, among which Nox2 mRNA was the most abundant. Pan-NADPH oxidase inhibitor VAS2870 (10 µM) significantly reduced arterial contractile responses to methoxamine. The inhibitors of Rho-kinase (Y27632, 3 µM), PKC (GF109203X, 10 µM) and Src-kinase (PP2, 10 µM), as well as LTCC blockers (nimodipine, 0.1 µM, and verapamil, 0.1 μM) also reduced methoxamine-induced contraction. Importantly, the effect of VAS2870 persisted in the presence of Rho-kinase, PKC or Src-kinase inhibitors, but not in the presence of LTCC blocker. Notably, the blockade of LTCC did not affect either basal or NADPH-induced O₂^•- production. Our data show that LTCC, but not Rho-kinase, PKC or Src-kinase are involved into procontractile effect of ROS, produced by NADPH oxidase, in saphenous artery of young rats. Сalcium influx through LTCC does not activate ROS production by NADPH oxidase.